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The box-type substation is playing an increasingly important role in the power network with its unique advantages.

Technical summary of box substation

I work in a comprehensive substation class in the daily installation of more and more box-type substations.

I. characteristics and types of box-type substation

The box-type substation is composed of high-voltage distribution device, power transformer and low-voltage distribution device, which are installed in a metal box. Each of the three parts occupies a space and is isolated from each other. The box-type substation is a relatively new type of equipment. It has developed from a relatively simple device to a more complete and reliable device now. It has the following advantages:

(1) it covers a small area and is convenient for land acquisition. It is suitable for installation in general urban areas with dense load, rural areas and residential areas, which is conducive to high-voltage extension, reducing the power supply radius of low-voltage lines and reducing line loss.

(4) can be used in the fully sealed transformer, SF6 ring network cabinet and other new equipment, with a long period, maintenance-free, fully functional features, can be used in the terminal, but also for the ring network.

(5) with novel and beautiful appearance, it is widely used for temporary power consumption in construction. The demand for power consumption in industrial parks, residential areas and commercial centers is in harmony with the environment.

The type of box substation can be divided into ordinary and compact type. The common type of box substation includes ZBW type and XWB type, etc., while the compact type of box substation includes zb1-336 type and GE box substation, etc. Fn12-12 or fzn25-12 load switches and fuses are commonly used in 10KV distribution devices of box-type substations, and are connected to the high-voltage end of transformers from adjacent overhead lines. Incoming wire can be cable or overhead insulated wire, according to the use of the environment and different purposes of arbitrary choice. When the box substation is used as an independent user, the primary power supply can be used.

1. Structural characteristics of ZBW type box substation. Zbw-10/0.4kv outdoor combined substation is a pre-installed complete set of transformer and distribution equipment which is composed of high voltage chamber, transformer chamber and low voltage chamber. Its features:

(1) it is applicable to the power supply mode of ring network, double line and terminal, and the three modes have excellent interchangeability. Incoming line adopts cable.

(3) the high-pressure chamber can be compatible with terminal load switch, air ring network switch, SF6 ring network cabinet, etc. Oil - immersed transformer and dry transformer can be used. The transformer room is temperature controlled and can be ventilated by natural ventilation or forced ventilation at the top.

(4) the low-voltage chamber is equipped with metering and reactive power compensation, and the secondary circuit and outlet number can be designed according to user needs to meet different needs.

(5) the shell is made of steel plate or alloy plate, with double top cover and good heat insulation. The shell and skeleton are all treated with anticorrosion, and have long-term outdoor conditions. The first library network appearance and color can be coordinated with the environment.

(6) it is easy to install. A cable room is set under the foundation of the box-type substation, and a manhole is set in the low-voltage city to enter the cable room for work.

(7) all rooms are separated into independent small rooms by partitions.

(8) for the convenience of monitoring and maintenance, there are lighting devices in each small room, and the lighting switch is controlled by the door.

2. Structure characteristics of GE box substation. The difference between American GE box substation and domestic combined box substation is that it is developed on the basis of transformer. GE box-type substation simplifies the structure of transformer core, high-voltage load switch, fuse and other equipment, and puts them into the same oil filling iron box. Its main structural features:

(1) it is small in size and compact in structure, and its occupation area is only about 1/3 of the domestic box-type substation of the same capacity.

(2) fully sealed, fully insulated structure, no insulation distance, reliable guarantee of personal safety. High voltage cable is connected to the sleeve with good insulation performance. The sleeve is connected to the elbow cable plug, and the live part is sealed in the insulation body.

Job summary

Summary of box substation technology (https://www.unjs.com). The elbow-type cable plug can be plugged or unplugged on line when the transformer is fully loaded, which is equivalent to a load switch. There are some wall hangers welded on the enclosure for fixing the pedestal type insulated bushing joint. When unplugging the elbow type cable plug, it can be inserted into the pedestal type bushing joint.

(3) GE box-type substation is protected by a backup protection fuse connected in series with a plug-in fuse. The backup protection fuse is installed in the box body, which is only used to protect the high-voltage line when the box substation has an internal phase fault. Plug - in fuse will fuse when short - circuit fault or over - load oil temperature is too high. This protection is economical, reliable and easy to operate.

(4) can be used for ring network, there can be used for the terminal. The four position conversion is convenient and the reliability of power supply is improved. In the specific selection, we need to pay attention to the switch's rated capacity, breaking capacity and dynamic, thermal stability level of the basic province grid match.

(5) strong overload capacity.

(6) the amorphous alloy transformer is adopted with small loss, and the wiring group is D and yn11. The low-voltage neutral point drift is small, and the lightning protection performance is good.

(7) the box adopts anticorrosive design and special spray paint treatment, which can be widely used in a variety of harsh environments, such as stormy and highly polluted areas.

3. Optional power supply mode of four position switches in GE box substation. The four position switches in the GE box substation have V type and T type. They can choose to switch on two power sources and the transformer at the same time or switch on one circuit. The model T four position switch allows the loop network to be maintained without excitation by the transformer. Both four-position switches have three-phase rotary mechanism, which can switch at rated current, but cannot be used to break the fault current.

The four-position switch needs to be operated with a special insulated operating lever, which can be rotated 360 in either direction to select the power supply mode. The four-position switch rotation mechanism is equipped with acceleration spring to ensure quick break or switch on and reduce the interruption time of power supply. Adjust the switch position indicator between the original position and the new position before operation. The action should be crisp and neat when operating, do not loosen in turning midway or stop, in order to prevent generation harmful arc, also cannot midway after stopping again reverse direction changes. When operating to the new position, the indicating switch should be slightly turned. When the "click" sound is heard, it indicates that the switch has entered the position, then the operating lever can be released and the operating lever can be returned to

2) compared with the initial value, the measured voltage under 1mA dc does not change more than 0.5%;

3) the leakage current under 75% of the measured voltage is no greater than 50uA;

4) resistive component and full current value: the resistive current or total current value of the continuous current of the operating current shall meet the requirements.

(3) 10KV four-position switch test item:

1) insulation resistance: use 2500 v shake table, not below 1000 m Ω;

2) ac withstand voltage of power frequency 42KV, 1min;

3) check the phase consistency of the circuit;

4) the function and position correctness of the four-position switch are checked and qualified.

Installation and operation requirements of various box-type substations

(1) the floor of the box-type substation should be placed on a higher place rather than in a low-lying place, so as to avoid the influence of rainwater into the box on the operation of the equipment. When pouring the concrete platform, the high and low pressure side should be left with space, which is convenient for laying the cable in and out. When excavating the foundation, it is necessary to dig the solid soil when the ground is accumulated by garbage or saprock, and then backfill the better soil and compaction, and then fill the three-ply soil or slush to ensure the foundation is stable.

(2) the grounding and zero wires of the box-type substation share a grounding network. Grounding network in the general foundation of the four corners of the grounding pile, and then connected into one. There must be two reliable connections between the box substation and the grounding grid. After the operation of the box-type substation, the grounding connection should be checked frequently, for it is not loose or corroded. Measured on a regular basis, grounding resistance grounding resistance should be not more than 4 Ω.

(3) the box-type substation is mainly cooled by natural wind circulation. Therefore, there should be no illegal accumulation around it, especially the door of the transformer room should not be blocked, and the fixtures on the ventilation hole of the shutter should be removed frequently to ensure that all electrical equipment does not exceed the maximum allowable temperature.

(4) after the low-voltage circuit breaker tripping, it shall check the tripping reason before sending it for trial. If the delivery is not successful, the cause of the fault must be thoroughly found, and then the power can be sent to prevent the expansion of the accident.

(5) a zinc oxide arrester shall be installed in the high-voltage distribution room of the box-type transformer. The installation method shall be convenient for testing, disassembly and replacement.

(6) the ring network switch, transformer, arrester and other equipment in the high-voltage distribution device shall be inspected and maintained regularly, repaired in time when defects are found, and insulation preventive test shall be carried out regularly. If the service period of the box-type substation exceeds 3 months, all preventive tests should be carried out before re-operation.

(7) to replace the hv fuse with no breaking capacity, the transformer must be cut off, the mechanical interlocking must be removed correctly during operation, and the insulated operating rod should be used. (8) all inlet and outlet cable holes of box substation shall be sealed to prevent small animals from entering and causing accidents. (9) it must have the warning sign of high voltage danger and the nameplate number of electrical equipment.

It is believed that with the development of electric power demand faster and faster box substation demand will also be more and more. With the improvement of technology, the box substation will become more perfect.